Joist



I. S. LELAND June 26, 1934.

JOIST Filed Feb. 8, 1952 BY kW ATTORNEY.

Patented June 25, 1934 umrsc STATES PATENT OFFICE JOIST Application February 8,

6 Claims.

The invention relates to joists and more particularly to an adjustable joist for supporting forms in concrete building construction or the like. For this purpose, lightness is essential and with this in mind, the present joist is designed with the View of making a maximum strength joist with a minimum amount of material.

In joists of the character described in which the lower chord is joined to the upper chord adjacent the supports, it has been the practice to provide an adjustable member for the ends of the joist adjacent the support. This construction is illustrated in the copending application of Russell W. Stambaugh and Walter E. Browne, Serial No. 423,438, filed January 25, 1930, and of which the present invention is an improvecut.

This construction has a decided disadvantage. With the intermediate section fixed and the overall length adjustable by extensible members on the ends of the span, a section relatively weak in bending moment is forced further away from the support into an area where the bending moment is comparatively high. This has necessitated the use of much heavier material in constructing the joist.

It is an object of the present invention, therefore, to provide an adjustable joist in which the adjustable feature is placed intermediate the ends of the truss and which will not in any way weaken the ultimate strength of the truss.

It is a further object of the present invention to provide a truss which is light and readily portable and which is economical to manufacture and easy to assemble.

It is another object of the invention to provide a truss to which intermediate sections of any length may be added and which is adapted to accommodate one or more intermediate sections, and further objects will become apparent upon consideration of the following specification.

A structure embodying the invention is illustrated in the accompanying drawing and will be hereinafter fully described, the invention re siding in certain novel features which will be particularly pointed out in the appended claims.

In the drawing:

Figure 1 is an elevational view of the joist;

Figure 2 is a perspective view looking at the joist from a point slightly above it;

Figure 3 is a detail view of the U-bolt;

Figure 4 is a cross section on the line 4-4 of Fig. 1, looking in the direction of the arrows.

1932, Serial No. 591,589

Referring to the accompanying drawing in which like numerals indicate like parts througi out the several views, the joist comprises a pair of end sections, generally designated 10, one or more intermediate sections 11 and adjustable connecting means generally designated 12.

The end sections comprise an upper chord 13 formed of a T beam, or, in heavier constructions, two angles back to back with the upper fiat surface thereof in a single plane. The inner end of the upper chord 13 is formed with a downwardly projecting mating plate 14 which forms a means for connecting the end section to the next adjacent section.

The lower chord 15 may be a similar T beam section, or may be any suitable tension member which will afford suirlcient area to make the connection between adjoining sections. The lower chord has a portion 15' parallel to the upper chord 13 and is bent upwardly towards the upper chord as shown at 16 and welded to the upper chord to form a solid support 17, upon which the end of the joist rests on the supporting structure.

The shear is absorbed by a continuous diagonal member 18 which zig-zags between the upper and lower chords, contacting the inturned legs of the Ts, at spaced points. A solid connection is formed between the diagonals and the upper and lower chords by welding the diagonals at the contacting points to the inturned legs of the T of the upper and lower chords respectively.

While it has been found advantageous to use a single continuous member for diagonal bracing, it will be understood that a plurality of diagonals may be used if desired.

One of the diagonal members may be provided with an angle 19 welded thereon and having an outstanding leg over which a U-bolt 20 is adapted to be retained and which will be described in detail below.

The intermediate sections 11 each comprise an upper chord 21 having a cross section similar to the upper chord 13 and terminating at the opposite ends in down-turned mating plates 22 which cooperate with the plates 14 to form supporting means for the connecting means 12.

The lower chord 23 of the intermediate section is similar in cross section to the lower chord of the end section and comprises a single straight piece running from one end of the section to the other.

A continuous diagonal member 24 zig-zags between the upper and lower chords, contacting the inturned edges of the T beams forming the upper and lower chords at spaced points where they are welded to form a rigid structure.

It has been found to be an advantage to terminate the diagonal members of the intermediate sections and the end sections adjacent the joint on one of the chords. While the diagonals l8 and 24 terminate on the lower chord, these members may also be terminated adjacent the joint on the upper chord, the advantage lying in terminating both of the diagonals of both the end intermediate sections adjacent the joint and on the same chord.

The connection 12 between the end sections 10 and the intermediate section 11 is made through the upper and lower chords. The upper chord may have a plurality of blocks 25 placed between the mating plates 14 and 22 to vary the length of the span. Bolts 26 pass through the blocks and through aligned apertures in the plates 14 and 22 to hold the blocks 25 assembled with the upper chords.

The lower chords are joined by tension members 2'? comprising a plurality of plates 2828 and 29. The plates 28 are similar in size and fit on the opposite sides of the vertical leg of the T. The plates 2828 and 29 have equally spaced holes 30 drilled therethrough, the holes being adapted to align with corresponding holes in the lower chords of the intermediate and end sections respectively. Bolts 31 pass through the aligned holes in the plates and in the lower chords to form the connection.

The size of the blocks 25 corresponds to the spacing of the holes 30 so that by removing one block, the lower chord is drawn up a distance of one hole to keep the upper and lower chords relatively the same length so that the entire top of the joist lies in a single plane.

For lighter loads, the joint 12 is sufficient to carry the shear accumulated between the diagonals. However, for heavier loads, a shear brace must be provided. This is ccomplished through the provision of the U-bolt 20 which loops over the top of the angle 19. A bar 32 has holes drilled therein and fits over the end of the U-bolt and abuts certain of the bolts 31. A pair of nuts 33 threaded on the legs of the U-bolt force the bar 32 against the bolts 31 to form a rigid di gonal member between the upper and lower chords in that space which is not provided with shear bracing.

t will be seen that this arrangement provides a joist in which the adjustable feature is placed intermediate the ends in a relatively strong portion of the beam and that this advantage has been accomplished without in any way weakening the ultimate strength of the joint.

Having thus described the invention, it is realized that it is susceptible to various changes and modifications coming well within the scope of one skilled in the art and it is not, therefore, desired to limit the invention to the precise form herein shown and described, but only by the scope of the appended claims.

What is claimed as new and desired to secure by Letters Patent is:

1. In a joist of the character described, including a plurality of independent and separable sections, each section comprising an upper chord, a lower chord and diagonal shear members, means readily detachably connecting the upper chord of one section to the upper chord of the adjacent section, means readily detachably connecting the lower chord of one section to the lower chord of the adjacent section, and a diagonal shear member connected to one section near its upper chord and to an adjacent section near the lower chord thereof.

2. In an adjustable joist of the character described, including a plurality of independent and separable sections, each of said sections comprising an upper chord, a lower chord and diagonal shear braces, an adjustable compression member connecting the upper chords of adjacent sections, an adjustable tension member connecting the lower chords of adjacent sections, said adjustable tension member cooperating with said adjustable compression member to vary the overall length of the span, and a diagonal shear brace connected to one section near its upper chord and to the adjacent section near its lower chord.

3. In a joist of the character described, including a plurality of separable sections, each section compri g an u; per chord, a lower chord and diagonal shear braces, means joining the upper chord of one of said sections to the upper chord of the adjacent section, means joining the lower chord of said first named section to the lower chord of the adjacent section, and a U-bolt connected to one of said sections near its upper chord and to the adjacent section near the lower chord to provide an auxiliary tie between its sections.

4. A skeleton beam comprising sections, said sections having upper and lower chords and a lattice work connecting the same, fillers between the ends of the upper chords of the sections, means to tie the end portions of the upper chords together with the fillers clamped therebetween and tension members tying the adjacent ends of the lower chords of the sections together.

5. A skeleton beam comprising sections, said sections having upper and lower chords and lattice work connecting the same, filler blocks located between adjacent ends of the upper chords of the sections, a tie bolt connecting the ends of said upper chords and holding the filler blocks in place, tie plates engaged with the adjacent ends of the lower chords of the sections, and bolts securing the tie plates to the lower chords.

6. A skeleton beam comprising sections, said sections having upper and lower chords and a lattice work connecting the same, fillers and a tie member connecting the upper chords of the sections, tie members connecting the lower chords of the sections, a brace yoke embracing the lattice of one section and having a cross bar abutting the other section, said brace yoke extending diagonally across the joint between the sections.

IRA S. LELAND 

